a) Field of the Invention
The present invention relates to a glass heating furnace, and more particularly to a glass heating furnace in which upper heating elements and lower heating elements are disposed in an alternating arrangement asymmetrically at an upper and lower position, and rollers rotate clockwise and counterclockwise, so that glass can be heated up more uniformly, thereby reducing effectively the thermal stress marks which are formed on the glass.
b) Description of the Prior Art
Glass is equipped with the excellent permeability and is scratch-proofed. Therefore, glass is widely used in a daily life, such as buildings and general articles for daily use. Furthermore, even in electronic products or vehicles, there are related glass products. Accordingly, it is apparently that the glass-related merchandises have already been everywhere in the people's life.
Glass is mostly made by the procedure of dosing, melting, forming and annealing. After making glass, glass can be also processed by an automatic apparatus such as a glass heating furnace. Glass is heated up by the glass heating furnace to improve the strength.
Referring to FIG. 1 and FIG. 2, a conventional glass heating furnace includes a chamber which is provided with plural upper heating elements 1 and lower heating elements 2 aligned symmetrically at an upper and lower position. In addition, plural rollers 3 are disposed between the upper heating elements 1 and the lower heating elements 2 to carry glass A. The glass A stays in the chamber for a fixed time at a fixed position and is heated up by the thermal radiation from the upper heating elements 1 and the lower heating elements 2. After being heated up for the fixed time at the fixed position, the glass A is driven by a roller power module 4 to be transmitted out of the chamber, and is then cooled down rapidly, thereby improving the strength. However, when the glass A receives the thermal radiation, the molecules in the glass will displace microscopically to be realigned and stacked with one another. Hence, if the glass A does not move at that fixed position, a part in the glass A directly below the upper heating elements 1 and directly above the lower heating elements 2 will be irradiated by the upper heating elements 1 and the lower heating elements 2 directly, resulting in a higher temperature at that part. This enables the glass molecules at that part to displace more easily and to be realigned and stacked with one another more tightly. On the other hand, for other area on the glass A which is not irradiated by the upper heating elements 1 and the lower heating elements 2 directly, such as the area that is not directly below the upper heating elements 1 and not directly above the lower heating elements 2, the temperature is lower in comparison with the part that is irradiated by the upper heating elements 1 and the lower heating elements 2 directly. This allows the glass molecules at that area to displace less easily and to be less easily realigned and stacked with one another, so that the molecules will be stacked less tightly comparing to the part that is irradiated by the upper heating elements 1 and the lower heating elements 2 directly. As the molecules are stacked more tightly at that part, the density in that part is higher; whereas, as the molecules are stacked less tightly at that area, the density in that area is lower. Therefore, the thermal stress marks will be formed by the heating due to the difference in density in the abovementioned two portions, and the refractive index will be different due to the difference in density. In addition, when light passes through the glass, the thermal stress marks in the glass can be identified visually due to the angle of refraction, thereby affecting the quality of uniformity for a same piece of glass.